Bulk acoustic resonator structure comprising hybrid electrodes

Abstract

In accordance with a representative embodiment, a BAW resonator structure, comprises a first BAW resonator, comprising: a first lower electrode having a first electrical resistance; a first upper electrode having a second electrical resistance; and a first piezoelectric layer disposed between the first lower electrode and the first upper electrode. The BAW resonator structure also comprises a second BAW resonator, comprising: a second lower electrode having the second electrical resistance; a second upper electrode having the first electrical resistance; and a second piezoelectric layer disposed between the second lower electrode and the second upper electrode. The BAW resonator structure also comprises an acoustic coupling layer disposed between the first BAW resonator and the second BAW resonator. The first electrical resistance is less than the second electrical resistance. An communication device comprising a coupled resonator filter (CRF) is also disclosed.

1. A BAW resonator structure, comprising:
 a first BAW resonator comprising: a first lower electrode having a first electrical resistance; a first upper electrode having a second electrical resistance; and a first piezoelectric layer disposed between the first lower electrode and the first upper electrode, wherein the first electrical resistance is less than the second electrical resistance; 
 a second BAW resonator comprising: a second lower electrode having the second electrical resistance; a second upper electrode having the first electrical resistance; and a second piezoelectric layer disposed between the second lower electrode and the second upper electrode wherein the first lower electrode and the second upper electrode each have a first acoustic impedance, the first upper electrode and the second lower electrode have a second acoustic impedance, and the first acoustic impedance is less than the second acoustic impedance; and 
 an acoustic coupling layer disposed between the first BAW resonator and the second BAW resonator, wherein the acoustic coupling layer has a third acoustic impedance, which is less than the first acoustic impedance, and a ratio of the second impedance to the third impedance is approximately 4.0 to approximately 100.0. 
 
     
     
       2. A BAW resonator structure as claimed in  claim 1 , wherein first lower electrode and the second upper electrode each comprise one of: molybdenum (Mo), or aluminum (Al), or platinum (Pt), or beryllium (Be), or silver (Ag). 
     
     
       3. A BAW resonator structure as claimed in  claim 1 , wherein the first upper electrode and the second lower electrode each comprise one of: tungsten (W), or ruthenium (Ru), or uranium (U 238 ), or osmium (Os). 
     
     
       4. A BAW resonator structure as claimed in  claim 1 , wherein the acoustic coupling layer comprises a single material. 
     
     
       5. A BAW resonator structure as claimed in  claim 1 , wherein the acoustic coupling layer comprises carbon-doped silicon oxide (SiOC). 
     
     
       6. A BAW resonator structure as claimed in  claim 1 , wherein the acoustic coupling layer comprises a silicon low-k resin. 
     
     
       7. A BAW resonator structure as claimed in  claim 1 , wherein the acoustic coupling layer comprises silicon oxynitride (SiO x N). 
     
     
       8. A BAW resonator structure as claimed in  claim 1 , wherein the BAW resonator structure comprises a coupled resonator filter (CRF). 
     
     
       9. A communication device, comprising:
 a transmitter; 
 a receiver; 
 a transmit filter connected to the transmitter; 
 a receive filter connected to the receiver, the receive filter comprising a coupled resonator filter (CRF), the CRF comprising: 
 a first BAW resonator comprising: a first lower electrode having a first electrical resistance; a first upper electrode having a second electrical resistance; and a first piezoelectric layer disposed between the first lower electrode and the first upper electrode; 
 a second BAW resonator comprising: a second lower electrode having the second electrical resistance; a second upper electrode having the first electrical resistance; and a second piezoelectric layer disposed between the second lower electrode and the second upper electrode; and 
 an acoustic coupling layer comprising silicon oxynitride (SiO x N) and disposed between the first BAW resonator and the second BAW resonator, wherein the first electrical resistance is less than the second electrical resistance. 
 
     
     
       10. A communication device as claimed in  claim 9 , wherein the first lower electrode and the second upper electrode each have a first acoustic impedance, the first upper electrode and the second lower electrode have a second acoustic impedance, and the first acoustic impedance is less than the second acoustic impedance. 
     
     
       11. A communication device as claimed in  claim 10 , wherein the acoustic coupling layer has a third acoustic impedance, which is less than the first acoustic impedance. 
     
     
       12. A communication device as claimed in  claim 11 , wherein the acoustic coupling layer comprises a single material. 
     
     
       13. A communication device as claimed in  claim 9 , wherein first lower electrode and the second upper electrode each comprise one of: molybdenum (Mo), or aluminum (Al), or platinum (Pt), or beryllium (Be), or silver (Ag). 
     
     
       14. A communication device as claimed in  claim 9 , wherein the first upper electrode and the second lower electrode each comprise one of: tungsten (W), or ruthenium (Ru), or uranium (U 238 ), or osmium (Os). 
     
     
       15. A communication device as claimed in  claim 9 , wherein the acoustic coupling layer comprises carbon-doped oxide (SiOC). 
     
     
       16. A communication device as claimed in  claim 9 , wherein the acoustic coupling layer comprises a silicon low-k resin. 
     
     
       17. A BAW resonator structure, comprising:
 a first BAW resonator comprising: a first lower electrode having a first electrical resistance; a first upper electrode having a second electrical resistance; and a first piezoelectric layer disposed between the first lower electrode and the first upper electrode; 
 a second BAW resonator comprising: a second lower electrode having the second electrical resistance; a second upper electrode having the first electrical resistance; and a second piezoelectric layer disposed between the second lower electrode and the second upper electrode, wherein the first electrical resistance is less than the second electrical resistance; and 
 a single layer of a single acoustic coupling material disposed between the first BAW resonator and the second BAW resonator, the single layer of the single material acoustic coupling layer having an inhomogeneous acoustic property across its thickness. 
 
     
     
       18. A BAW resonator structure as claimed in  claim 17 , wherein the inhomogeneous acoustic property is acoustic impedance.